The present invention relates generally to an arrangement for, and a method of, expeditiously adjusting one or more reading parameters of an imaging reader operative for reading targets by image capture over a range of working distances based on target distance, especially in an imaging reader having an aiming light assembly offset from an imaging assembly.
Solid-state imaging systems or imaging readers have been used, in both handheld and/or hands-free modes of operation, to electro-optically read targets, such as one- and two-dimensional bar code symbol targets, and/or non-symbol targets, such as documents. A handheld imaging reader includes a housing having a handle held by an operator, and an imaging module, also known as a scan engine, supported by the housing and aimed by the operator at a target during reading. The imaging module includes an imaging assembly having a solid-state imager or imaging sensor with an imaging array of photocells or light sensors, which correspond to image elements or pixels in an imaging field of view of the imager, and an imaging lens assembly for capturing return light scattered and/or reflected from the target being imaged, and for projecting the return light onto the array to initiate capture of an image of the target. Such an imager may include a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device and associated circuits for producing and processing electronic signals corresponding to a one- or two-dimensional array of pixel data over the imaging field of view. In order to increase the amount of the return light captured by the array, for example, in dimly lit environments, the imaging module generally also includes an illuminating light assembly for illuminating the target, preferably with a variable level of illumination light for reflection and scattering from the target. An aiming light assembly may also be supported by the imaging module for projecting a visible aiming light spot on the target.
In some applications, for example, in warehouses, it is sometimes necessary for the same reader to read not only far-out targets, e.g., on products located on high overhead shelves, which are located at a far-out range of working distances on the order of thirty to fifty feet away from the reader, but also close-in targets, e.g., on products located at floor level or close to the operator, which are located at a close-in range of working distances on the order of less than two feet away from the reader. A near imager may be provided in the reader for imaging and focusing on close-in targets over a relatively wider imaging field of view, and a far imager may also be provided in the same reader for imaging and focusing on far-out targets over a relatively narrower imaging field of view. Typically, at least one of the imagers, usually the far imager, has a variable focus, such as a movable lens assembly or a variable focus element.
Although the known imaging reader is generally satisfactory for its intended purpose, it can be challenging for the reader to expeditiously select the correct imager to read a target, to expeditiously select the correct gain and/or exposure for the selected imager, as well as to expeditiously select a correct level of illumination to illuminate the target that can be located anywhere in the extended working distance range. It can also be challenging to focus the correct imager over the extended working distance range. Contrast-based automatic focusing, which is common in consumer cameras on smartphones, is notoriously slow, because it relies on capturing and processing many images over many successive frames over a relatively long time period to determine the best focus position. Such sluggish performance is not acceptable in many industrial applications where a fast-acting, aggressive, and dynamic reader is desired.
Accordingly, there is a need to expeditiously adjust various reading parameters of an imaging reader, such as selecting the correct imager, adjusting the gain and/or exposure of at least one imager, adjusting the illumination level, and focusing the at least one imager, for reading a target that can be located anywhere in an extended working distance range relative to an imaging reader, without slowing or degrading reader performance.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and locations of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The arrangement and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.